Vehicles for battlefield use by infantry typically include armored personnel carriers manned by several combat soldiers. These vehicles carry protective armor plating to allow the occupants to traverse areas under moderate enemy fire with a minimum of battle casualties. The vehicles normally are equipped with small caliber weapons such as 20 millimeter automatic canon and one or more 30 caliber or 50 caliber machine guns. Such canons are useful mainly against enemy vehicles of the same type mentioned, but at a limited range such as 500 meters insofar as armor piercing capability using conventional 20 mm AP projectiles. Machine guns such as mentioned are useful mainly for deterrent effect over relatively medium range limited areas of terrain and are ineffective either against point targets or multiple targets dispersed at wide angles.
Both of the foregoing limitations of existing small arms weapons render them unsuitable for massed troop attacks such as encountered in the Korea and Vietnam conflicts. This tactic operates simply to present more moving targets at one time and place than either long or short range guns firing conventional ammunition can address individually or collectively. This problem is further compounded when such massed multiple targets further include multiple levels of vulnerability as for example flesh targets and protective armor plate, at close range as well as relatively distant range during closure of battle forces in a typical direct encounter.
The 20 mm high explosive round does not become armed until after it traverses 40 to 50 meters from the muzzle, hence provides no defense against massed personnel attacks within a range of 50 meters. The 20 mm armor piercing round is not effective against such attacks at any range, because it is point target limited and can address only a few points with each burst. In addition, it is not performance reliable beyond 500 meters against armored targets.